PRP preparation changes what is in the shot

The clinic can describe the prepared blood in plain words

Ask how much blood is taken and how much prepared blood returns in the shot. The clinic may count the clot-forming platelets after spinning. Otherwise, it may give only the range its machine usually makes.

Also ask whether your shot keeps many white cells, the blood cells that fight germs. These answers describe your prepared blood but can’t predict relief because bigger blood counts aren’t a promise.

Your comfort matters more than a large count.

White cells may affect soreness after the shot

Some methods keep more germ-fighting white cells, while other methods remove more. Research suggests that more of these cells may cause more soreness after a joint shot. It does not prove the best amount for every joint or tendon.

Clinics may also make clot-forming platelets release their repair signals before the shot. A blood test can show that release, but it can’t show whether you will move better later.

The machine’s brand does not answer that question.

Medicine changes belong with the prescribing clinician

A test of prepared blood found that low-dose aspirin changed some repair signals from clot-forming platelets. The test did not show whether that change helped or harmed a sore joint, and it did not support stopping aspirin.

Tell the clinic about every prescription, drugstore medicine, and supplement you take. Ask the clinician who prescribed each drug before making a change. Waiting on PRP may be safer than stopping an important medicine.

Your regular clinician remains part of this choice.

Sources

1. A systematic review of 105 clinical PRP studies in orthopaedics published 2006-2016 found that only 11 (10%) described the preparation protocol clearly enough for another investigator to repeat it, and only 17 (16%) reported any quantitative metric of the final PRP composition. The authors concluded that the current reporting of PRP preparation and composition does not allow the PRP products actually delivered to patients to be compared between studies.

   Chahla J, Cinque ME, Piuzzi NS, et al. — A Call for Standardization in Platelet-Rich Plasma Preparation Protocols and Composition Reporting: A Systematic Review of the Clinical Orthopaedic Literature. Journal of Bone and Joint Surgery (American), 2017. DOI: 10.2106/JBJS.16.01374.

2. A systematic review that screened 876 studies and extracted standardised data from 33 commercially available PRP systems and protocols found that final product concentrations of platelets, white cells and growth factors varied widely between systems, as did the preparation protocols themselves. Platelet concentration correlated directly with the volume of blood drawn and with the centrifugal force of the device. The authors called the heterogeneity between separation systems something that 'must be resolved for proper study of this promising treatment'.

   Fadadu PP, Mazzola AJ, Hunter CW, et al. — Review of concentration yields in commercially available platelet-rich plasma (PRP) systems: a call for PRP standardization. Regional Anesthesia and Pain Medicine, 2019. DOI: 10.1136/rapm-2018-100356.

3. The PAW classification was proposed because PRP preparation protocols 'vary widely between authors and are often not well documented in the literature, making results difficult to compare or replicate'. It sorts preparations by three variables: the absolute number of Platelets, the manner of Activation, and the presence or absence of White cells - the three levers that make two injections both called 'PRP' materially different products.

   DeLong JM, Russell RP, Mazzocca AD — Platelet-rich plasma: the PAW classification system. Arthroscopy, 2012. DOI: 10.1016/j.arthro.2012.04.148.

4. In a controlled laboratory study, blood from five healthy donors was processed through three commercial PRP systems (MTF Cascade, Arteriocyte Magellan, Biomet GPS III). Platelet, red-cell and TGF-beta1 concentrations did not differ significantly between systems, but white-cell counts and PDGF-alpha-beta, PDGF-beta-beta and VEGF concentrations differed significantly across all three. Cascade produced leukocyte-poor PRP while GPS III and Magellan produced leukocyte-rich PRP with correspondingly higher white cells and growth factors.

   Castillo TN, Pouliot MA, Kim HJ, et al. — Comparison of growth factor and platelet concentration from commercial platelet-rich plasma separation systems. American Journal of Sports Medicine, 2011. DOI: 10.1177/0363546510387517.

5. A narrative review of PRP concluded that the literature suggests leukocyte-rich PRP is more beneficial in tendinopathies while pure (leukocyte-poor) PRP is more beneficial in cartilage pathology - but stated plainly that different PRP preparations have not been directly compared head-to-head in ANY pathology, and that the PRP type used is frequently not even stated in published research.

   Collins T, Alexander D, Barkatali B — Platelet-rich plasma: a narrative review. EFORT Open Reviews, 2021. DOI: 10.1302/2058-5241.6.200017.

6. A prospective fixed-sequence controlled laboratory study in healthy men found that daily low-dose aspirin significantly reduced release of VEGF, PDGF-AB and TGF-beta1 from freshly isolated leukocyte-rich PRP when activated with arachidonic acid. This is the mechanistic basis for the routine instruction to review antiplatelet and NSAID use before a PRP draw - and the authors noted clinical studies are still needed to establish how much this matters in vivo.

   Jayaram P, Yeh P, Patel SJ, et al. — Effects of Aspirin on Growth Factor Release From Freshly Isolated Leukocyte-Rich Platelet-Rich Plasma in Healthy Men: A Prospective Fixed-Sequence Controlled Laboratory Study. American Journal of Sports Medicine, 2019. DOI: 10.1177/0363546519827294.